Process and equipment for manufacture of advanced composite structures

ABSTRACT

A process for continuous, tailored lamination of aligned composite materials in such a way that either pre-formed or pre-consolidated sheets are made available for subsequent infusion molding or stamping processes, the process comprising the steps of: material placement, consolidation/stabilization, cut and kit, fabrication, and final trim. A tailored blank machine is also described. The blank machine includes a series of material placement heads arranged in a linear or serial fashion along a single moving placement table, wherein each head lays down a single angle of the prescribed stacking sequence as the conveyer passes under the head at a constant speed wherein the angle is proportional to head traverse rate divided by conveyer speed.

This application is a continuation of U.S. patent application Ser. No.11/113,978, filed Apr. 26, 2005, which is a continuation of U.S. patentapplication Ser. No. 10/443,964, filed May 23, 2003, now U.S. Pat. No.6,939,423, which is a continuation of U.S. patent application Ser. No.09/916,254, filed Jul. 30, 2001, now U.S. Pat. No. 6,607,626, whichclaims the benefit of U.S. Provisional Application No. 60/221,517, filedJul. 28, 2000, all of which are herein incorporated by reference intheir entirety.

FIELD OF THE INVENTION

The present invention addresses the affordable manufacture of advancedcomposite automotive structures using repeatable, monitorable,versatile, and production friendly approaches and processes.

BACKGROUND

The use of advanced composites, defined herein as highly alignedreinforcements of carbon, glass, or aramid fibers in a suitable polymermatrix of either thermoset or thermoplastic resins, is the focus of thisinvention. The specific intent to use aligned reinforcement is based onthe following perception: The modulus of steel is 30,000,000 lbs/in²,whereas the modulus of aluminum is 10,000,000 lbs/in². The modulus of atypical, higher quality glass epoxy prepreg is around 4,000,000 lbs/in².While material stiffness can be compensated to some degree via theshaping of the components to enhance structural stability, randomlyreinforced composite materials currently being used by the automotiveindustry have even less stiffness and therefore do not offer thepotential for dramatic improvements in structural performance.

For composites to be exploited in the design of an automobile, theirunique characteristics must be incorporated into both the design and theproduction scenario of the vehicle in a way that allows their inherentadvantages to be realized.

SUMMARY OF THE INVENTION

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

In another aspect, the present invention provides methods and techniquesfor integrating the production demands of higher volume automotivestructures with the higher performance available from advanced compositematerials, in a way that yields repeatable, affordable performance. Theinvention provides processes for continuous, tailored lamination ofaligned composite materials in such a way that either pre-formed orpre-consolidated sheets are made available for subsequent infusionmolding or stamping processes respectively. The infusion processes arenot unlike those already in widespread use such as resin transfermolding (RTM) or vacuum assisted resin transfer molding (VARTM). Thestamping process is not unlike what is currently used to stamp steelautomotive structures. For either approach, liquid infusion or solidstate stamping, component design must be tailored to the processes toachieve performance and cost goals. The concept incorporates aspects ofseveral available technologies including fiber or tape placement,stretch-broken and commingled fiber yarns, binderized pre-forming,heated consolidation, and NC cutting and kitting. The process that isthe subject of this invention can be used with either thermoplastic orthermoset matrix resins by manipulating the various options inherent ineach process step of the invention.

Advantages to this invention are that it addresses fundamental elementsrequired if a breakthrough in affordable high performance and highvolume advanced composite automotive structures are to become a reality.Issues this invention successfully address are: 1) the need for minimaltouch labor between part design and near-finished part, 2) highlyrepeatable, tailorable, versatile, and controllable processes, 3)minimization of scrap materials during fabrication, 4) in-line processmonitoring and control (to minimize post-inspection and scrappedfinished components), 5) delivery of “advanced composite” performancevia aligned “continuous”-like fibrous reinforcement, 6) ability tohandle the lay-up of many laminate architectures using the sameequipment and switch between lay-ups readily to manage and balanceproduction leveling for a range of model variants etc., and 7) in-lineapproach to applying other materials and value added functionality suchas sound and vibration dampening, paintless coloring and finish,integral trim surfaces, among other benefits.

Accordingly, the present invention is directed to a process andequipment for manufacture of advanced composite structures.

An object of the present invention is to produce large aligned carbonreinforced components that assemble easily.

Another object of the present invention is to improve the speed andefficiency of production every year.

Another object of the present invention is to create a repeatable andconsistent process in terms of quality, performance, mass, fit andfunction.

Another object of the present invention is to eliminate conventionalpainting.

Another object of the present invention is to balance capital investmentwith production rate and volume.

Another object of the present invention is to have a logical approach tomaterials handling and inventory.

Another object of the present invention is to seek a solution thatminimizes scrap.

Another object of the present invention is to start with materials asclose to raw material forms as possible.

Another object of the present invention is to automate as much aspossible.

Another object of the present invention is to maintain a safe, clean,and manageable production environment.

Another object of the present invention is to incorporate aligned carbonreinforcement.

Another object of the present invention is to control laminatearchitecture.

Another object of the present invention is to tailor the componentdesign to the unique aspects of the manufacturing process beingconsidered.

Another object of the present invention is to consider the extremes ofusing the same laminate, thickness, and material everywhere.

Another object of the present invention is to utilize flexibility interms of risk, starting materials, and quality achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. In the drawings:

FIG. 1 is an isometric view of a preferred embodiment of a structuremade in accordance with the present invention.

FIG. 2 is an exploded isometric view of parts of the structure made inaccordance with the present invention.

FIG. 3 is a schematic diagram of preferred embodiment of a materialplacement step in accordance with the present invention.

FIG. 4 is a schematic diagram of preferred embodiment of other steps inthe process in accordance with the present invention.

FIG. 5 is a schematic diagram of preferred embodiment of other steps inthe process in accordance with the present invention.

FIG. 6 is a schematic diagram of a preferred embodiment of a materialplacement station in accordance with the present invention.

FIG. 7 is an enlarged isometric schematic view of a head in accordancewith the present invention.

FIG. 8 is a bottom view of a preferred embodiment of a head inaccordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

FIG. 1 shows an isometric view of a body structure 100 made inaccordance with the present invention.

As shown in FIG. 2, the body structure is preferably divided into anumber of parts. The boundaries of these parts are preferably selectedto facilitate manufacture. One way to facilitate manufacture of theparts is to create parts that can be referred to as being “globallyplanar,” meaning that their overall shapes are as flat as possible.Complex overall geometries are achieved by combining more geometricallysimple parts, as shown in FIG. 2. Such parts are more amenable to theprocess described herein because the blanks have to deform less toconform to the desired part shape. Globally planar parts also havesimpler tooling.

All of the parts shown in FIG. 2 can be made according to the presentinvention. However, for purposes of clarity, this disclosure focuses onthe manufacture of one part 202. Again, it should be kept in mind thatevery part shown in FIG. 2 and any other suitable part can be made inaccordance with the present invention.

The process preferably begins by selecting the materials that areintended to be used in making the composite part. The starting materialsinclude discontinuous aligned carbon fiber tow with a handling binder.This would typically be supplied in creels, or spools, for dispensing.Other fiber types (such as glass or aramid) and formats (such ascontinuous) could also be used. For the liquid infusion fabricationprocesses, the process that is the subject of this invention wouldutilize continuous tow reinforcement or discontinuous tow reinforcement,with a binder compatible with the intended matrix resin. For the solidstate fabrication processes, the process that is the subject of thisinvention would utilize continuous tow reinforcement or discontinuoustow reinforcement pre-impregnated with the intended matrix resin, orpre-impregnated tape comprised of continuous or discontinuous towreinforcement and the intended matrix resin. The choice of materialswill be entirely interdependent with the design and complexity of theintended end component, with discontinuous tow reinforcement arequirement for even subtle geometries. The impregnation in either casecould be in the form of hot melt, solvent, for thermoset orthermoplastic matrices, or commingling of for thermoplastic matrixresins.

For the reinforcement material form, options include discontinuouspreimpregnated carbon tape; discontinuous preimpregnated carbon tow withthermoplastic; binderized discontinuous carbon fiber tow; binderizedfabric strips comprised of discontinuous carbon fiber tow; andcontinuous carbon fiber tow.

For the matrix material, options include most thermoplastics and somethermosets that meet automotive requirements such as environmentalstability (temperature, humidity, corrosives, etc.) cost, surfacequality, toughness, and recyclability.

After the starting materials, or stock materials have been selected, thematerials are associated with one another and assembled in the mannershown schematically in FIGS. 3-5, which show the preferred steps used ina preferred embodiment of a process according to the present invention.The process is preferably capable of being fully automated, withprogramming tailored to the intended finished components and directlylinked to three dimensional part design software and databases such ascommonly used in the automotive and aerospace industries. The steps aredescribed individually with parallel discussion of potential processvariations illustrating the versatility of the invention in.

FIG. 3 shows an early step of the process, the material placement step302. As shown in FIG. 3, the process preferably includes at least onematerial placement station 306, preferably more than one materialplacement station is used. In an exemplary embodiment of the presentinvention, six material placement stations 306, 308, 310, 312, 314, and316 are used.

Referring to FIG. 6, each material placement station can be moved in adirection 602 that is different than the direction of motion 604 ofconveyor 304. For clarity, FIG. 6 shows only one placement station 306.It should be kept in mind that the other placement stations 308, 310,312, 314, and 316 can also move in a manner similar to placement station306. In an exemplary embodiment of present invention, the placementstations move in a direction 602 that is perpendicular to the motion 604of conveyor 304.

Material placement station 306 preferably includes a plurality of heads606. Preferably heads 606 are disposed in a direction similar to thedirection of motion 602.

Referring to FIG. 7, each of the heads 606 includes a rotating portion702. This permits head 606 to dispense a material 704 in a variety ofdirections relative to head 606. FIG. 8 shows a bottom view of head 606and rotating portion 702. The relative orientation of material 704 canbe seen with respect to rotating portion 702.

Given this arrangement, the material placement stations 306 are able todispense a plurality of materials 704. This plurality of materialassumes the configuration of a sheet when disposed by placement station306. By selectively rotating heads 606 and moving placement station 306,the material can be dispensed in a variety of orientations anddirections. The invention also contemplates that different placementstations, for example, station 306 and 308 (see FIG. 3) will dispensematerial in directions different than one another.

Heads 606 can also provide discontinuous material feed. In other words,the material dispensed by head 606 can be turned on or turned off whendesired.

Returning to FIG. 3, as the different placement stations 306, 308, 310,312, 314 and 316 dispense material, different plies having differentorientations of fibers or material can be observed.

Once a component has been designed with this production process in mind,the laminate architecture and flat plane layout (developed blank) of thedesired end component may be sent to a pre-processing software program.This program generates an NC machine program for the tailored blankmachine that is part of the subject of this invention.

The result of the combination of the moving table and the series ofheads (several may be required for each ply in the stack) is continuousproduction of laminated sheet with the specific lay-up programmed forthat particular run of sheet that could be either 1) consolidated undera hot roller with carefully controlled pressure application and a seriesof rollers and heat zones to produce near fully consolidated laminatedsheet for solid state stamping fabrication approaches, or 2) a drybinderized laminated sheet for liquid infusion fabrication processes.The capability of the placement heads could allow starting and stoppingof the materials to allow for cutouts such as doors and windows, whichwill reduce materials scrap, which could be a significant source ofcost. A potential variation of the tape laying head that may providefurther cost benefits, is to use “chopper gun” to place highly alignedplies down on the moving table, with each gun laying up an individualangled ply as would the placement head. The gun could potentially laydown all the material forms discussed in the section of this document.

Several options and modifications can be made to the material placementstep. At the ply level, placement options include: 1) placement headplays out the tape from a roll mounted to the head, heats it as it movesthrough the head, and further at the point of application via a heatedplacement roller, and places it in NC programmed locations on the movingbelt; 2) placement head aligns numerous preimpregnated tows to create a“tape” just before point of application, and places it in NC programmedlocations on the moving belt; 3) placement head impregnates numerousbinderized tows, aligns them to create a tape just before the point ofapplication, and places it in NC programmed locations on the movingbelt; 4) placement head plays out the fabric strip from a roll, heats itin the head and further at the point of application via a heatedplacement roller, and places the material in NC programmed locations onthe moving belt; 5) placement head aligns numerous binderized tows,heats them to create a binderized tape just before the point ofapplication, and places it in NC programmed locations on the movingbelt; and 6) placement head chops the carbon fiber tow on the fly, andplaces the discontinuous fibers on the moving table in an alignedfashion. In option 6), binder powders are distributed uniformly eitheron the fly or once the ply is completely laid down.

At the laminate level, multiple placement stations are required, eachusing an identical head technology. The number of stations required isdetermined by the desired production rate, the number of plies, angles,and special details, and the selected starting material form. Each headwould place material per the NC program to lay down a single ply at agiven angle. Once a given point on the belt has moved through all theactivated placement stations, the result is a laminate of the desiredcombination of number of plies and respective angles, including pad-upsand other special reinforcements. Entire operation is NC controlled andcapable of switching to a different vehicle variant as product pullsystem mandates.

The consolidation stage 402 comprises a series of heated consolidationrollers that compresses the laminate stack to a desired level ofconsolidation and thickness. A variation of this approach is to placebinderized tows into a band of highly aligned dry fibers at theprescribed angle. Binderizing powders (a resin powder that is chemicallycompatible with the intended matrix resin) could be deposited betweenthe plies as well if required. After the final ply is laid down, athermal compaction step could be applied to hold the fibers in theirproper position prior to subsequent processing steps. The resultantsheet could then be cut and kitted if it is destined for a liquidinfusion fabrication process. If the material is to be used in astamping operation, an additional step of liquid infusion andconsolidation, much like a pultrusion or extrusion process, could beapplied to fully impregnate and consolidate the laminate prior to cutand kit. This kit could then be used in a solid state stampingfabrication process. Consolidation, if required, would be performed atthe end of the laminating operation using a series of heated and cooledrollers. This step would be tailored to the intended final fabricationprocess as discussed briefly in the previous paragraph.

Other options that are available at this step include:

1) The laminate stack is run through a series of heated rollers underincreasing pressures to fully consolidate the laminate stack.

2) The laminate stack is run through a “stabilization” zone thatincludes a heated zone and mild compaction roller that simply applies auniform through thickness temperature to knit all the plies together toenable subsequent handling of the kitted laminates. The stack must bestable enough to go through a dry forming operation (if required formore complex geometries) yet remain lofty enough to enable adequateresin flow in the subsequent liquid infusion processing step thatproduces the finished component.

The cut and kit stage 404 and 406 comprises an NC controlled ultrasoniccutting machine (or similar technology) that cuts each tailored blankfrom the moving belt and sends the blank to either a fabrication cell orinto a staging area. This stage is similar to NC ultrasonic cuttingstations widely used in the aerospace industry.

Regardless of the end use, liquid infusion molding, solid statestamping, or other, the laminated stack can be cut and kit intopredefined bins for delivery to the final processing cell. Additionalelements of the final component, such as adhesives sheets, coloreddecals, or fittings etc. could be added to the bins prior to deliver tothe final processing cell.

Ink jet identification technology is entirely compatible with theprocesses described as part of the subject of this invention. They canbe employed at any point along the length of tailored blank machine andat the cut and kit portion of the overall process to provide materialand part ID, as well as fabrication instructions for the finalproduction process used to make the final component.

The process can employ ultrasonic NC controlled cut and kit: each“tailored blank” is cut from the moving belt and kitted with the otherlaminates required for a complete body set, then sent to the fabricationcell to be turned into a final component. Other cutting technologiescould be applied as well.

The component fabrication step (for the solid state fabrication processillustrated) includes a pre-processing and molding station. A pre-heatshuttle 502 would be utilized to heat the laminate stack to the desiredtemperature and then rapidly shuttle the stack between the tools in thestamping press. The second station is a single stage heated stamping die504 will clamp the perimeter of the laminated sheet and stamp thecomponent. After stamping, the stamping tool is rapidly cooled from 220°C. to below glass transition temperature, then demolded.

Starting with a bin of kitted flat tailored blanks, properly identifiedusing ink-jet and/or bar code tracking technology, the final fabricationprocess imparts the shape and final curing and/or consolidation of thecomponent. Fabrication cells are arranged as shown in. Each cellidentifies the process steps required to proceed to the next cell in thesequence, along with key cell parameters that effect cost and timing.Fabrication steps comprise best industry practice for either solid statestamping or liquid infusion, with process parameters tailored to bestexploit this invention.

Preprocessing options include: 1) a pre-heat shuttle would be utilizedto heat the laminate stack to the desired temperature and then rapidlyshuttle the stack between the stamping dies, and 2) a pre-formingoperation that utilizes a simple heated forming tool similar to a press(but not nearly so accurate and with minimal applied pressure) that canform the binderized laminate into a near net shape, prior to theinfusion operation. In addition, some components may require embeddedhard points or other pre-placed details.

Processing options include solid state and liquid infusion methods. Forsolid state, a single stage heated stamping die will clamp the perimeterof the laminated sheet and stamp the component. For liquid infusion, thebinderized laminate goes straight into the heated infusion tool, thetool is closed which forces the stack into the shape of the closedcavity, and the matrix resin injected.

For solidification/curing, the tools remain at temperature until thecomponent is cured for thermosets. If thermoplastic, the tool is rapidlycooled to just below the Tg, then demolded.

The final step is a robotic trim station using conventional high speedrouters with low horsepower. Drills would be high speed with a low feedto reduce back side breakout. Both drills and routers will be floodedwith water for fiber control and cooling. Robotic pick and placetechnology 508 would be used in conjunction with vacuum jigs andfixtures to maintain rate and repeatability.

Final trim operations 506 involve high speed routing in vacuum chuckedjigs as per best industry practice for high performance advancedcomposite structures. Robotic trim station using conventional high speedrouters with low horsepower. Drills would be high speed with a low feedto reduce back side breakout. Both drills and routers will be floodedwith water for fiber control and cooling.

The foregoing disclosure of embodiments of the present invention hasbeen presented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formsdisclosed. Many variations and modifications of the embodimentsdescribed herein will be obvious to one of ordinary skill in the art inlight of the above disclosure. The scope of the invention is to bedefined only by the claims appended hereto, and by their equivalents.

1. A tailored blank comprising a first group of fibers and a secondgroup of fibers, the tailored blank obtained by carrying out a processcomprising: providing a first relative displacement between a dispensinghead and a table while dispensing through the dispensing head onto thetable the first group of fibers, such that the first group of fibers isaligned in a direction determined by the first relative displacement;turning the dispensing head on and off to intermittently dispense thefirst group of fibers; providing a second relative displacement betweenthe dispensing head and the table while dispensing through thedispensing head onto the first group of fibers the second group offibers, such that the second group of fibers is dispensed at an angle tothe direction, the angle determined by the second relative displacement;and turning the dispensing head on and off to intermittently dispensethe second group of fibers.
 2. The tailored blank of claim 1, theprocess further comprising consolidating the first group of fibers andthe second group of fibers.
 3. The tailored blank of claim 1, theprocess further comprising dispensing a matrix material along with thefirst group of fibers and the second group of fibers.
 4. The tailoredblank of claim 1, the intermittent dispensing of the first group offibers and the second group of fibers forming an opening in the tailoredblank.
 5. The tailored blank of claim 1, the first group of fiberscomprising one of glass, aramid, carbon fiber preimpregnated tape,preimpregnated carbon tow, binderized discontinuous carbon fiber tow,binderized fabric strips comprised of discontinuous carbon fiber tow,and continuous carbon fiber tow.
 6. The tailored blank of claim 1, theprocess further comprising applying, by ink jet, fabricationinstructions to the tailored blank, the fabrication instructionsdisclosing a process by which to form the tailored blank into acomposite part.
 7. The tailored blank of claim 1, the process furthercomprising dispensing a binder along with the first group of fibers andthe second group of fibers.
 8. A method for manufacturing a tailoredblank from which to fabricate a composite part, the tailored blankcomprising a first group of fibers and a second group of fibers, themethod comprising: dispensing the first group of fibers along a firstdirection; stopping the dispensing of the first group of fibers alongthe first direction to form an opening; resuming the dispensing of thefirst group of fibers along the first direction after the opening;dispensing the second group of fibers on the first group of fibers alonga second direction that is at an angle to the first direction; stoppingthe dispensing of the second group of fibers along the second directionat the opening; and resuming the dispensing of the second group offibers along the second direction after the opening.